Synthetic silver halide emulsion binder

ABSTRACT

A photosensitive silver halide emulsion wherein the emulsion binder comprises a graft copolymer of a quaternary ammonium alkyl acrylate salt on a polyhydroxy-substituted polymer.

United States Patent 1191 Fitzgerald June 11, 1974 SYNTHETIC SILVER HALIDE EMULSION 3.425.836 2/1969 Perry ct a1. 96/114 BINDER 3,681,079 8/1972 Fitzgerald 96/114 3.709.690 l/1973 Cohen et al. 96/114 [75] Inventor: Maurice J- tzg rald, Cant 3.749.577 7/1973 Hollister et a1. 96/114 Mass.

[73] Assignee: Polaroid Corporation, Cambridge,

Mass Puma/y ExammerRonald H. Sm1th Assistant ExaminerRichard L. Schilling [22] Flled: Jan. 2, 1973 [21] Appl. No.: 320,450

52 us. c1 96/114, 96/107 R, 96/113, [57} ABSTRACT 96/120 G036 603C H28, G036 1/02 A photosensitive silver halide emulsion wherein the [58] Field of Search 96/114, 1 14.3, 1 i3 emulsion ind r mpris s a graft copolymer of a quaternary ammonium alkyl acrylate salt on a polyhy- [56] Ref r Cit d droxy-substituted polymer.

UNlTED STATES PATENTS 2.839.401 6/1958 23 Claims, No Drawings Gray et a1. 96/114 1 SYNTHETIC SILVER HALIDE EMULSION BINDER BACKGROUND OF THE INVENTION This invention relates to photography and more particularly, to novel photosensitive photographic elements, particularly novel photosensitive emulsions.

As a result of the known disadvantages of gelatin, in particular, its variable photographic properties and its fixed physical properties, for example, its diffusion characteristics; much effort has been expended in the past in order to replace gelatin with a suitable synthetic colloid binder for photographic silver halide emulsions. Many synthetic polymeric materials have heretofore been suggested as peptizers for silver halide emulsions, however, these have generally not functioned satisfactorily and frequently have not fulfilled all of the basic requirements for a photosensitive silver halide emulsion binder listed following:

1. absent (or constant) photographic activity;

2. ability to form an adsorption layer on microcrystals of silver halide permitting stable suspensions to be obtained; I 3. ability to form adsorption layers as described in 2 above which do not prevent growth of silver halide microcrystals during physical ripening; and

4. solubility in water solution.

In addition, hithertofore, much emphasis has been placed on the ability of the synthetic polymeric material to mix with gelatin, as this property has been critical for employment in partial substitution reactions with gelatin. Consequently, many synthetic polymers of the prior art have been materials which allow for the growth of silver halide crystals only. in the presence of gelatin.

Graft copolymers of various types have been employed in the prior art as gelatin substitutes in photographic silver halide emulsions; however, these copolymers have included monomers quite different from those employed in the present invention.

For example, Caldwell US. Pat. No. 2,843,562 discloses graft copolymers of vinyl chloride on polyvinyl alcohol and related vinyl alcohol polymers; Perry and Reynolds US. Pat. No. 3,425,836 describes graft copolymers suitable for silver halide dispersions in the preparation of photographic emulsions wherein a quaternary ammonium vinyl ether monomer is grafted onto a hydrophilic polysaccharide; and my US. Pat.

-No. 3,681,079. describes a graft copolymer emulsion binder wherein an aminoalkyl acrylate monomer is grafted onto a polyhydroxy substituted polymer.

SUMMARY OF THE INVENTION The present invention is directed to a photosensitive silver halide emulsion wherein the silver halide crystals are disposed in a synthetic polymeric binder comprising a water-soluble film-forming graft copolymer of a quaternary ammonium alkyl acrylate monomer represented by the formula:

wherein R, is hydrogen, a lower alkyl group, i.e., 1-4 carbon alkyl group, preferably methyl or ethyl, or a halogen, i.e., chloro, bromo, or iodo; R is hydrogen, a lower alkyl group, a halogen or cyano group; R is a lower alkylene, i.e., 1-4 carbon alkylene group or a lower cycloalkylene group, i.e., 3-6 carbon cycloalkylene group; and R R and R each is a lower alkyl or a lower cycloalkyl group, i.e., a 3-6 carbon cycloalkyl group; or R and/or R and/or R and/or R taken together represent the atoms necessary to complete a 3 to S-membered heterocyclic ring structure; and X is a salt-forming anion, e.g., halide, sulfate, alkylsulfonate, arylsulfonate, nitrate, etc.; on a poly hydroxy substituted polymer.

If desired, the graft copolymer may also include a second monomer grafted thereon, i.e., an ethylenically unsaturated monomer. In still another embodiment, the above-described polymer may comprise only a portion of the binder, the remainder constituting gelatin or a second synthetic polymer.

DETAILED DESCRIPTION OF THE INVENTION As indicated, the present invention is directed to photosensitive silver halide emulsions wherein photosensitive silver halide crystals are disposed in a watersoluble film-forming synthetic polymeric binder comprising a poly hydroxy-substituted polymer having grafted thereon a quaternary ammonium alkyl acrylate monomer represented by the formula set forth above. The term filmforming is intended to designate a molecular weight sufficiently high to form a film, for example, a molecular weight comparable to that of gelatin (i.e., around 15,000).

The polymers of the present invention have been found to substantially meet all of the basic requirements of a gelatin substitute without possessing the above-described deficiencies of gelatin. More specifically, the emulsions of the present invention are more stable against degradation than gelatin; particularly against hydrolysis of the polymeric backbone in acidic or basic media. Theemulsions of this invention also show a resistance to the growth of microorganisms which is not exhibited by gelatin.

An important feature of the graft copolymers of this invention is the presence of a mobile anion or counter-ion which is free to diffuse in the aqueous medium of the silver halide emulsion. This counter-ion may thus be used to introduce a photographically advantageous reagent into the emulsion, for example, by providing a counter-ion which is a photographic sensitizer, antifoggant, stabilizer or the like. Of course, the counter-ion should be selected by one practicing this invention so as to be compatible with the silver halide emulsion and its intended usage; for example, if a silver bromide emulsion were contemplated, one would not use a poly meric binder with an iodide counter-ion since the greater insolubility of the silver iodide would result in the precipitation of silver iodide in preference to silver bromide.

With regard to the backbone polymer of the graft copolymer; in general, any organic polymer comprising repeating units comprising structural units containing a plurality of groupings capable of being oxidized by, e.g., a transition metal ion catalyst is useful in the present invention. Preferred backbones are substituted or unsubstituted cellulosic or polyvinyl polymers, and most preferably, a backbone selected from the group consisting of polymeric polyols, polyvinyl alcohol, gelatin, polysaccharides, partial acetals of polyvinyl alcohol, etc.

It is believed that upon oxidation of the grouping, the free radical is formed, which attacks the double bond of the quaternary ammonium salt monomer, thus initiating polymerization.

As examples of such polyhydroxy-substituted polymers, mention may be made of the following:

1) cHioa OH CHzOH cellulose CHaOCHzCOOH H J F 'l OH O OH 0 OH CH 0H carboxymethylccllulose M v V 0 43H, 0 OOH carboxymethyl hydroxyethyl cellulose (s) O OH I OCH: (3H OH; 0H CH1 0-CH, JHCH;

CH2 0 CH3 0-0113 hydrcxybutylmethyl cellulose COOH OOH

alglnie acid OH O O OCHaJ3HCHa Lambda carragecnin scluble starch gelatin Poly-y-N-(B-hydroxypropyl)-L-glutamide 1 -CO0H polyglutamlc acid GH,CH;CHOH

Poly-a-chlorovlnyl 'y-hydrcxypropyl ether CH1 (IJHCHa OH Polya-bromovinyl fl-hydroxy-n-propyl ether (40) emon Polyvinyl hydroxymethy] ketone 6 NH: H2CHJOH 1:1 copolymer of acrylamidezisopropenyl B-hydroxyethyl ketone C Cal I 1 emon NH, cmcmcmon 1:1 copolymer oi aerylamiderq-chlorovinyl 'y-hydroxypropyl ketone Poiy-N-vinylpyrrolidone As examples of monomers represented'by the formula:

R1 R2 (III-1:5 :0

6 R. R5 I hi% .X

wherein R R R R R R and X have the aboveindicated definitions and which are contemplated as being useful for employment in the instant invention for grafting onto the polyhydroxy-substituted polymer, mention may be made of thefollowing:

' cm cm cm=cn oo o-on i N 1 acryloyloxy methyl trimethyl ammonium chloride 2-(a-chloroacryloyloxy)ethyl trimothyl ammonium p-toiuenesulfonate fi-(methacryloyloxy)ethyi(ethyl dimethyl ammonium) ethyl sulfate 50. CH; CH CH: CH;

6 J: CH --COOCH HCHz-IIIQ C1 cH,=oH-c 0 O-N(3H, .01 N -methy1-3-acryloyloxyquinuclidinium chloride CH =OH C O 0CH|CH:-N .I

N-[B-(aeryioyloxy) ethyl] quinuclidinium iodide 53 CE; C H

4-(acryloyloxy)cyclohexyl trimethyl ammonium p-toluenesulionate The instant graft copolymers may have, in addition to the structures defined above, any compatible repeating unit or various repeating units or additional grafted segments which are not detrimental to photographic silver halide emulsions and which permit the polymers to be soluble in water. Examples of typical comonomers which may be employed include the following ethylenically-unsaturated monomers:

acrylic acid methacrylic acid 56.

(I11 CHFC-OOOH zaias zl i; Eda 57.

Br CH1 =(LCOOH a-bromoacr ylic acid 58. CH3CH=CH-COOl-i crotonic acid 59. CH CH=CHC OOH isocrotonic acid isopropenyl bromoacetate 130. CH =Cl-l--OOC-C-CH vinyl pivalate 1 3 1 CH =CHNHCOOC-(CH N-vinyl-tertiary butylcarbamate EXAMPLE 1 1:5 graft copolymer of l3-(methacryloyloxy)ethyl tri- 132. CH =CCHz-COCH2CH a methylammomum methyl sulfate on polyvinyl alco- COOH ho] ethylwarbcxya'butemte 100 mls. of a 10 percent aqueous solution of polyvi- 133. nyl alcohol (commercially available from E. l. duPont deNemours and Company, Wilmington, Del., under the crri-=cH' 15 designation Elvanol 70-05), 20.25 g. of B(methai H cryloyloxy)ethy1 trimethylammonium methyl sulfate (commercially available from Alcolac Chemical Corp., 134. Baltimore, Md., under the designation Sipomer Q5) and 1.5 g. of Ce(Nl-l (NO catalyst were added to' CHT=CH-COOCH1 0 a 250 ml. three-neck round-bottom flask set up with nitrogen circulation. The pH of the resultant solution was a acry1oyloXymethy1/tetrahydrofuran then adjusted to 1.5 with HNO and stirred overnight with a stream of nitrogen bubbling through the solu- 135. tion. The polymer was then precipitated in acetone,

CHFCHTQTOH collected and dried under vacuum at 45 C. The yelp-hvdroxystyrene low-white water-soluble powder was analyzed by com-- bustion analysis based on nitrogen and sulfur to contain CH2=CH 1 part Sipomer Q-5 for every 5 parts of polyvinyl alcohol. I

EXAMPLES n xii 137. The procedure of Example I was employed to produce a series of graft copolymers of- B-(methacryloylox- 0H y)ethyl trimethylammonium methyl sulfate (monomer) 9:l =t! .n o 35 f I W EXAMPLES ll Xll Molar ratio of monomer to Quantity of Quantity Quantity polyvinyl alcohol 10% solution of of by combustion Description Example polyvinyl alcohol monomer Ce(NH (N 3)u analysis of product 11 100 mls. 20.25 g. 3.0 g. 1:7 yellow-white powder 111 100 mls. 40.50 g. 1.5 g. 1:12 white powder IV 25 mls. 20.25 g. 0.19 g. 613,7 yellow powder V 100 mls. 81.00 g. 1.5 g. 5:29 light-brown powder V1 100 mls. 81.00 g. 3.0 g. 1:4 ye1low-white powder V11 25 mls. 40.50 g. 0.19 g. 3:86 yellow powder VH1 25 mls. 40.50 g. 0.375 g. 4:23 white powder 1X 25 mls. 40.50 g. 0.75 g. 2:7 yellow powder X 12.5 mls. 40.50 g. 0.375 g. 6:17 yellow powder X1 100 mls. 40.50 g. 3.0 g. 1:6 yellow-white powder X11 12.5 mls. 40.50 g. 0.19 g. 3:65 yellow powder 138. Q 7 EXAMPLE Xlll CH=CH -ooo1r I Graft copolymer of 3-(methacryloyloxy)-2- --Harbxytmw hydroxyprop-l-yl trimethylammonium chloride CH and isopropyl acrylamide on polyvinyl alcohol 2 63 g. of isopropyl acrylamide and 10 g. of 3- C O OH (methacryloyloxy)-2-hydroxypropl -yl trimethylamm 1,arlmwswmm monium chloride (commercially available from the aforementioned Alcolac Chemical Corporation under I= the designation Sipomer Q-l) were added with stirring to a solution of 1 l g. of polyvinyl alcohol in 500 cc. of water at 50 C. and under nitrogen. Nitrogen was bub- QiQQYlQEFY 'X XHW. 65 bled through the solution for 1 hour, the pH adjusted Polymerization of the indicated monomers is achieved by conventional transition metal ion catalyst techniques.

to 1.5 with HNO and then 1.1 g. of Ce(Nl-l (NO catalyst in 10 cc. of water was added. Stirring of the solution was continued for 2 hours and the resultant viscous liquid was diluted with 250 cc. of water. The liquid product was analyzed to have 9.3 percent solids and a residual isopropyl acrylamide content of 0.1 g./l.

The following general procedure may be used for preparing photographic emulsions using the abovedescribed polymeric salts of the instant invention as the colloid binders.

A water-soluble silver salt, such as silver nitrate, may be reacted with at least one water-soluble halide,- such as potassium, sodium, or ammonium bromide, preferably together with potassium, sodium or ammonium iodide, in an aqueous solution of the polymer. The emulsion of silver halide thus-formed contains water-soluble salts, as a by-product of the double decomposition reaction, in addition to any unreacted excess of the initial salts. 'To remove these soluble materials, the emulsion may be centrifuged and washed with distilled water to a low conductance. The emulsion may then be redispersed in distilled water. To an aliquot of this emulsion may be added a known quantity of a solution of bodying or thickening polymer, such as polyvinyl alcohol having an average molecular weight of about 100,000 (commercially available from E. I. duPont'deNemours & Company, Wilmington, Del., designated Type 72-60). A surfactant, such as dioctyl ester of sodium sulfosuccinic acid, designated Aerosol OT, (commercially available from American Cyanamid Company, New York, N.Y.), may be added and the emulsion coated onto a film base of cellulose triacetate sheet having a coating of hardened gelatin.

The emulsions may be chemically sensitized with sulfur compounds such as sodium thiosulfate or thiosulfate or thiourea, with reducing substances such as stannous chloride; with salts of noble metals such as gold, rhodium and platinum; with amines and polyamines; with quaternary ammonium compounds such as alkyla-picolinium bromide; and with polyethylene glycols and derivatives thereof. a

The polymers employed as the binders in the emulsions of the present invention may be cross-linked according to conventional procedures. As an example, the polymers may be ionically cross-linked with a dibasic acid or cross-linked with succinaldehyde. Crosslinking agents conventionally employed with hydroxylcontaining polymers, such as boric acid, may also be employed. 5

The emulsions of the present invention may also be optically sensitized with cyanine and merocyanine dyes. Where desired, suitable antifoggants, toners, restrainers, developers, accelerators, preservatives, coating aids, plasticizers, hardeners and/or stabilizers may be included in the composition of the emulsion.

The emulsions of this invention may be coated and processed according to conventional procedures of the art. They may be coated, for example, onto various types of rigid or flexible supports, such as glass, paper, metal, and polymeric films of both the synthetic type and those derived from naturally occurring products. As examples of specific materials which may serve as supports, mention may be made of paper, aluminum, polymethacrylic acid, methyl and ethyl esters, vinylchloride polymers, polyvinyl acetal, polyamides such as nylon, polyesters such as polymeric film derived from ethylene glycol-terephthalic acid, and cellulose derivatives such as cellulose acetate, triacetate, nitrate, propionate, butyrate, acetate propionate, and acetate butyrate. Suitable subcoats may be provided on the supports, for example, a layer of gelatin, if necessary or desirable for adherence, as is well known in the art.

The polymers employed in the practice of the instant invention may contain about 5 to mole percent of the grafted monomer, preferably about 20 mole percent. The specific amount employed may be selected by the operator depending upon the grain particle size and habit desired. For example, the grain size 'distribu tion of the emulsion may be varied by changing the mole ratio and type of monomer grafted on the hydroxyl-containing polymer backbone.

By selecting appropriate comonomers, the copolymers of this invention may be made to be compatible with all water-soluble bodying polymers. Emulsions made from these novel polymers may be bodied with any water-soluble polymers, overcoming the disadvantage encountered with gelatin which is only compatible with a very few polymers in a most limited pH range. As examples of specific materials which may serve as bodying polymers are gelatin, polyvinyl alcohol, polyacrylamide, polyalkylacrylamides, polyvinyl pyrrolidone, polymethacrylamidoacetamide, vinyl alcohol/N- vinylpyrrolidone copolymers, poly-N-ethylaziridine, poly-N-(2-hydroxyethyl) aziridine, poly-N-(2- cyanoethyl) aziridine, poly (fi-hydroxy-ethyl acrylate), polyethylene imine and cellulose derivitives such as hydroxyethyl cellulose, hydroxypropyl cellulose and methyl cellulose. It has been found that using only a small amount of one or more of the graft copolymers, large amounts of photosensitive silver halide grains may be obtained. An emulsion made from one of the graft copolymers may therefore be bodied with a watersoluble polymer such that the polymeric constitution of the resulting emulsion comprises a relatively large percentage of the bodying polymer.

By selecting appropriate comonomers, copolymers with selected diffusion characteristics may be prepared. For example, the rate of diffusion of alkali ion or a dye-developer through an emulsion comprising one of the polymers of this invention may be modified by varying the composition of the polymer.

The preparation and photographic utilization of the instant invention will be further illustrated by reference to the following non-limiting examples.

EXAMPLE XIV Silver halide emulsions employing the polymers of Examples I-X ascolloid binders were prepared by the following procedure. 7 V V A solution of 4. 15 g. of the dry graft polymer in 266 ml. of distilled water was adjusted to pH 3.0 with dilute nitric acid and maintained at a temperature of 55 C. To this solution, 88.0 g. of dry potassium bromide and 1.0 g. of dry potassium iodide were added.

A solution of 55 g. of silver nitrate in 500 ml. of distilled water was prepared. From this silver nitrate solution, ml. was rapidly added with continuous agitation to the polymer-halide solution and the remainder was added over a period of 22 minutes. Thereafter, the emulsion was ripened for 60 minutes at 55 C., and then rapidly cooled to below 20 C.

EXAMPLE XV Silver halide emulsions employing the polymers of Examples XI and XII as the colloid binders were prepared by the procedure of Example XIV, except that the quantities of all reagents were one-half those of Example XIV when the polymer of Example XI was used and one-quarter those of Example XIV when the polymer of Example XII was used.

EXAMPLE XVI A sliver halide emulsion employing the polymer of Example XIII as the colloid binder was prepared by the following procedure.

mington, Del., designated Type 72-60) at a silver to polymer ratio of about 1:0.74. The remaining aliquots received no bodying polymer solution. A surfactant, Aerosol OT, was added and each emulsion aliquot was A solution comprising 43.62 g. of the liquid graft co- 5 slot coated at various silver coverages onto a base of polymer (at 9.3 percent s lids) in 266 ml of di till d cellulose triacetate sheet 5 mils thick subcoated with water was adjusted to pH 6.5 with dilute nitric acid and 30 mg/Sq. ft. of hardened gelatin. This film so prepared 7 maintained at a temperature of 28 C. To this solution, as ir ried. xpo ed on a sensitometer. n pr 440 g. of dry potassium bromide and 0.50 g. of dry poed with a processing solution and an imagetassium iodide were added. 10 receiving sheet from a Polaroid Type 107 Land film as A solution of 55 g. of silver nitrate in 500 ml. of dissembly (Polaroid Corporation, Cambridge, Mass). tilled water was prepared. From this silver nitrate solu- The negative and image-receiving elements were maintion, 100 ml. was rapidly added to the polymer-halide tained in superposed position for 10 seconds after solution and the remainder was added over a period of which hey re ripp part- Al ern i ly. h pr 22 minutes. Thereafter, the emulsion wasripened for cessing was effected with a processing solution and an minutes at 28 C., with continuous agitation, at the image-receiving element from a Polaroid Type 42 Land end of which it was rapidly cooled to below 20 C. film. The photographic characteristics of the resulting positive prints were then measured by an automatic re- EXAMPLE XVII (Control) cording densitometer. The following table summarizes A silver halide emulsion employing gelatin as the 001- 20 the densitometer readings obtained on samples of these loid binder was prepared according to the procedure of prints:

TABLE 2 Ag/Bodying Grain-growing Bodying Polymer mg/Ag Film Polymer Polymer Ratio ft. System D, D AD l3:l:5.9 graft copolymer 1 none m 71.3 T-42 1.76 0.03 1.73 of N-isopropyl acrylamide and 3-(methacryloyloxy)-2- hydroxyprop-l-yl trimethylammonium chloride do. do. do. do. T-107 1.73 0.01 1.72 do. polyvinyl 10.74 67.8 T-42 -1.71 0.39 1.32

alcohol NO. 72-06 do. do. do. do. 'r-107 1.76 0.11 1.65

Example XVI, except that 4.15 g. of dry gelatin was In certain photographic applications, it may be desiradded to the 266 mls. of distilled water and the emulsion was ripened at a temperature of C.

The following table summarizes the silver halide grain sizes obtained in the emulsions prepared above. All emulsions contained octahedral platelet crystals.

able to replace part, but not all, of the gelatin in the photosensitive emulsion. In view of the characteristics of these polymers described above, and further, in view of their compatability with gelatin in substantially all 40 proportions, it will be obvious that these polymers are ideally suited for such use.

TABLE 1 Grain Size {microns} Examples Polymer Range Average I and XIV 1:5 graft copolymer of fi-(methacryloyloxy) ethyl 0.2-0.8 0.4

trimethylammonium methyl sulfate on polyvinyl alcohol 11 and XIV 1:7 graft copolymer of the above materials 0.2-1 .4 0.6 III and XIV 1:12 graft copolymer of the above materials 0.3-1.2 0.5 IV and XIV 6:37 graft copolymer of the above materials 0.3-1.6 0.6 V and XIV 5:29 graft copolymer of the above materials 0.2-1.7 0.7 VI and XIV 1:4 graft copolymer of the above materials 0.3-1.6 0.7 VII and XIV 3:86 graft copolymer of the above materials 0.3-2.4 0.6 VIII and XIV 4:23 graft copolymer of the above materials 0.3-1.3 0.6 IX and XIV 2:7 graft copolymer of the above materials 0.2-1.2 0.4 X and XIV 6:17 graft copolymer of the above materials 0.4-1.2 0.6 XI and XV 1:6 graft copolymer of the above materials 0.2-1.0 0.5 X11 and XV 3:65 graft copolymer of the above materials 0.4-1.2 0.5 XIII and XVI 13:15.9 graft copolymer of N-isopropyl acrylamide 0.4

and 3-( methacryloyloxy )-2-hydroxyprop- I -yl trimethylammonium chloride on polyvinyl alcohol XVII gelatin 0.2-1.8 1.0

EXAMPLE XVIII The term photosensitive and other terms of similar import are herein employed in the generic sense to describe materials possessing physical and chemical properties which enable them to form usable images when photo-exposed by radiation actinic to silver halide.

Since certain changes may be made in the above products and processes without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description shall be interpreted as illustrative only and not in a limiting sense.

.What is claimed is: g

I. A photosensitive silver halide emulsion wherein the emulsion binder comprises a water-soluble filmwherein R is hydrogen, a lower alkyl group or a halogen; R2 is hydrogen, a lower alkyl group, a halogen or cyano group; R is a lower alkylene or lower cycloalkylene group; R R and R each is a lower alkyl group or a lower cycloalkyl group, or R and/or R and/or R and/or R taken togetherrepresent the atoms necessary to complete a 3 to S-membered heterocyclic ring structure; and X is a salt-forming anion.

2. The product as defined in claim 1 wherein substantially all of said emulsion binder comprises said graft copolymer.

3. The product as defined in claim 1 wherein said graft copolymer comprises about 5 to 75 mole percent of said monomer.

4. The product as defined in claim 3 wherein said graft copolymer comprises about mole percent of said monomer.

5. The product as defined in claim 1 wherein said silver halide emulsion is a silver iodobromide emulsion.

6. The product as defined in claim 1 wherein said emulsion includes at least one chemical sensitizing agent.

7. The product as defined in claim 1 wherein said emulsion includes at least one optical sensitizing agent.

8. The product as defined in claim 1 wherein said monomer is 3-(methacryloyloxy-2-hydroxyprop-l-yl trimethylammonium chloride.

9. The product as defined in claim 1 wherein said monomer is B-(methacryloyloxy)ethyl trimethylammoniummethyl sulfate.

10. The product as defined in claim 1 wherein said polyhydroxy-substituted polymer is polyvinyl alcohol.

11. The product as defined in claim 1 wherein said graft copolymer includes a second ethylenically unsaturated monomer.

12. The product as defined in claim 11 wherein said second monomer is acrylamide.

13. The product as defined in claim 11 wherein said second monomer is N-isopropyl acrylamide.

14. The product as defined in claim 1 wherein said emulsion includes a bodying polymer.

15. The product as defined in claim 14 wherein said bodying polymer is gelatin.

l6. The product as defined in claim 14 wherein said bodying polymer is polyvinyl alcohol. I

17. 'A method of preparing a photosensitive silver halide emulsion which comprises reacting a watersoluble silver salt with a water-soluble halide salt in an aqueous solution containing a water-soluble filmforming graft copolymer of a polyhydroxy-substituted polymer having grafted thereon a monomer of the formula:

wherein R is hydrogen, a lower alkyl group or a halogen; R is hydrogen, a lower alkyl group, a halogen or cyano group; R is a lower alkylene or lower cycloalkylene group; R R and R each is a lower alkyl group or a lower cycloalkyl group, or R and/or R and/or R and/0r R taken together represent the atoms necessary to complete a 3 to 8-membered heterocyclic ring structure; and X is a salt-forming anion.

18. The method as defined in claim 17 wherein said monomer is 3-(methacryloyloxy)-2-hydroxyprop-l -yl trimethylammonium chloride.

19. The method as defined in claim 17 wherein said monomer is B-(methacryloyloxy)ethyl trimethylammonium methyl sulfate.

20. The method as defined in claim 17 wherein said polyhydroxy-substituted polymer is polyvinyl alcohol.

21. The method as defined in claim 17 wherein said graft copolymer includes a second ethylenically unsaturated monomer.

22. The method as defined in claim 21 wherein said second monomer is acrylamide. v

23. The method as defined in claim 20 wherein said second monomer is N-isopropyl acrylamide. 

2. The product as defined in claim 1 wherein substantially all of said emulsion binder comprises said graft copolymer.
 3. The product as defined in claim 1 wherein said graft copolymer comprises about 5 to 75 mole percent of said monomer.
 4. The product as defined in claim 3 wherein said graft copolymer comprises about 20 mole percent of said monomer.
 5. The product as defined in claim 1 wherein said silver halide emulsion is a silver iodobromide emulsion.
 6. The product as defined in claim 1 wherein said emulsion includes at least one chemical sensitizing agent.
 7. The product as defined in claim 1 wherein said emulsion includes at least one optical sensitizing agent.
 8. THe product as defined in claim 1 wherein said monomer is 3-(methacryloyloxy-2-hydroxyprop-1-yl trimethylammonium chloride.
 9. The product as defined in claim 1 wherein said monomer is Beta -(methacryloyloxy)ethyl trimethylammoniummethyl sulfate.
 10. The product as defined in claim 1 wherein said polyhydroxy-substituted polymer is polyvinyl alcohol.
 11. The product as defined in claim 1 wherein said graft copolymer includes a second ethylenically unsaturated monomer.
 12. The product as defined in claim 11 wherein said second monomer is acrylamide.
 13. The product as defined in claim 11 wherein said second monomer is N-isopropyl acrylamide.
 14. The product as defined in claim 1 wherein said emulsion includes a bodying polymer.
 15. The product as defined in claim 14 wherein said bodying polymer is gelatin.
 16. The product as defined in claim 14 wherein said bodying polymer is polyvinyl alcohol.
 17. A method of preparing a photosensitive silver halide emulsion which comprises reacting a water-soluble silver salt with a water-soluble halide salt in an aqueous solution containing a water-soluble film-forming graft copolymer of a polyhydroxy-substituted polymer having grafted thereon a monomer of the formula:
 18. The method as defined in claim 17 wherein said monomer is 3-(methacryloyloxy)-2-hydroxyprop-1-yl trimethylammonium chloride.
 19. The method as defined in claim 17 wherein said monomer is Beta -(methacryloyloxy)ethyl trimethylammonium methyl sulfate.
 20. The method as defined in claim 17 wherein said polyhydroxy-substituted polymer is polyvinyl alcohol.
 21. The method as defined in claim 17 wherein said graft copolymer includes a second ethylenically unsaturated monomer.
 22. The method as defined in claim 21 wherein said second monomer is acrylamide.
 23. The method as defined in claim 20 wherein said second monomer is N-isopropyl acrylamide. 